Process for the recovery of wool wax from wool scour liquor froths



Jan. 21, 1958 L. F. EVANS ETAL' 2,820,803

PROCESS FOR THE RECOVERY OF woor. WAX FROM WOOL SCOUR LIQUOR FROTHS Filed Sept. 18, 1953 9 RELATION OF ACID NUMBER 8 OF CENTRIFUGED WAX TO THE PH OF THE DI5PER5lON ACID NUMBER OF WAX United rates PROCESS FOR THE RECOVERY OF WOOL WAX FROM WOOL SCOUR LIQUOR FROTHS Application September 18, 1953, Serial No. 381,029

11 Claims. (Cl. 260-4125) This invention relates to the recovery of wool wax from the froths which are produced as a first stage in the recovery of wool wax from wool scour liquor. It is known to recover the wool wax from this froth by treatment in an autoclave but the results are not very satisfactory. We have found that by the use of sodium carbonate as a dispersing reagent some froths can be converted into a dispersion of such a form that the wax can be separated by centrifuging, but this method is not dependable and with some froths it does not work at all.

The object of this invention is to provide a process of treating these froths which will enable much more dependable results to be obtained by centrifuging. According to this invention the froth is treated with one or more sodium or potassium phosphates as a dispersing agent and the pH of the dispersion, unless raised sufiiciently by the phosphates, is adjusted by adding sodium carbonate or other alkaline material. The desired pH depends upon the nature of the detergent used in the scouring of the wool. It may also be adjusted, especially when soaps are used in the scouring, to control the acid number of the resultant Wax. The acid content of the resultant Wax is derived mainly from the hydrolysis of the soap, where soap is used as the detergent. The term soap, unless otherwise qualified, is intended to mean one or more of the alkali metal salts of the higher fatty acids such as the stearates, palmitates and oleates (which are long chain soaps). The acid content of the resultant wax is also derived, but to a much lesser extent, from the hydrolysis of the short chain suint soaps present in the scour liquor. The adjustment of pH is explained subsequently. The Wax can be separated readily from the resultant dispersion by centrifuging after the dispersion has been heated to a temperature of at least about 85 C.

As sodium phosphates are less expensive than potassium phosphates they are more suitable for use in this process. It has been found that suitable phosphates are disodium hydrogen phosphate, sodium dihydrogen phosphate, tettasodium pyrophosphate (marketed under the trademark Tetron) and the complex sodium polyphosphate marketed under the trademark Calgon.

The aims of the process are to obtain a high recovery of the wax which is present in the froth, and usually to produce wax of an acid number less than 1 (i. e. which requires less than 1 mgm. of potassium hydroxide to neutralise 1 gm. of wax). In some cases it may be desirable for commercial reasons to produce a wax having an acid number somewhat higher than 1 but normally it is desirable for the wax to have as low an acid numher as possible. The recovery of the wax depends upon the composition of the solution and to some extent upon the physical treatment of the dispersion, e. g. the amount of stirring to which it is subjected. Although a low acid number is normally desirable the recovery may be better with a higher acid number.

The froth which is submitted to this treatment may atent ice be produced satisfactorily by a flotation process. This froth may be produced from wool scour liquors where soap has been used as the detergent or from those where synthetic detergents have been used; thus non-ionic detergents of the condensed ethylene oxide type or anionic detergents of the sulphated long chain alcohol type give wool scour liquors from which the froths can be treated by this process. Examples of these twotypes of synthetic detergents are, respectively, the detergent marketed under the trademark Lissapol N and that marketed under the trademark Teepol.

In the case where soap has been used as the detergent the froth may contain about 10-20% Wool wax, 1-2% soap and a little dirt. This froth, after addition of sodium carbonate or other alkaline material to bring the pH to the correct point as hereinafter explained, and after addition of the phosphate, is heated to at least about C. and a dispersion is produced from which the wax can be separated readily. This separation will be effected by centrifuging.

The accompanying drawing is a graph in which the pH of the dispersion of a froth from a soap scour liquor is plotted against the acid number of the resultant wax. In this graph the points 1 show the specific results of experimental tests and the curve 2 indicates the mean of these results. It will be seen from this curve that to obtain any one of the acid numbers set out in the following table the pH should be adjusted approximately to the value set out in the same horizontal line of that table.

TABLE Acid No. of wax pH of dispersion Approximately 10.2. Approximately 9.8 or more. Approximately 9.3. Approximately 8.4. Approximately 7.7.

These acid numbers, however, obviously depend somewhat on the soap content of the original froth.

To obtain wax having acid numbers of 0.5 and less the following solutions give good recoveries of wax.

(a) /21% sodium carbonate plus 0.05 to 0.5% (optimum 0.1 to 0.2%) disodium hydrogen phosphate.

(b) /21% sodium carbonate plus 0.1 to 0.5% (optimum 0.1 to 0.2%) Tetron. The recovery falls off markedly at 0.5% Tetron and at 0.7% Tetron no wax is recovered.

(c) /2-1% sodium carbonate plus (1.2-0.5 Calgon. With this amount of sodium carbonate the optimum amount of Calgon will not exceed 0.5 but if more sodium carbonate is used more Calgon can be used Without lowering the pH below 10.

An alternative specification of the above solutions would be that the sodium carbonate should be enough to give a pH of about 10.2 or higher.

To obtain Wax having an acid number of about i the following solutions give good recoveries:

(1) 1% Tetron with no added sodium carbonate. Recoveries fall off when more than .05% sodium carbonate is added.

(2) 0.2-3.0% Calgon plus sodium carbonate to give a pH of about 9.8.

For higher acid numbers solutions of Tetrou or disodium hydrogen phosphate could be used with the pH adjusted to the corresponding value as shown on the graph by adding either sulphuric or phosphoric acids or sodium dihydrogen phosphate. Disodium hydrogen phosphate alone in 1% solution gave a pH about 9.1 and an acid number about 3, whereas a mixture of disodium hydrogen phosphate (1%) and sodium dihydrogen phosphate (1%) gave a pH about 7.7 and an acid number as high as depending somewhat on the composition of the original froth. One advantage of the more acid conditions, was. that the, wax. dispersion. creamed and separated. very readily.

When treating froths. resulting from wool scour liquors produced with the synthetic detergents abovementioned adjustment of the pH of the. dispersion is not so. necessary as whenv soap is used. as.- the detergent. As an example, with LissapolN as thedetergent and 0.2% Calgon. as the phosphate content the pH of the. dispersion was 6.5 and the wax acid. number was 1.75. As another example, with Teepol as the detergent. and 1% Tetron as the phosphate content the pH of the dispersionwas 9.6, and. the wax acid numberwas 0.6..

In some, cases, and especially where soap has been used as the detergent, a second centrifuging is desirable, to reduce the water content ofthe wax, and the effect of this second centrifuging is more marked than is the case where the froth is not treated with. a phosphate in accordance with this invention. It is advantageoustocool the wax from the first centrifuging and to reeheat it' before subjecting it to the second centrifuging.

We. claim:

1. Process for the recovery of wool wax. from; froths.

produced from wool scour liquor, which comprises treating the froth with a dispersing agent selected from the group consisting of sodium phosphates and potassium phosphates, heating the dispersion to a temperature of at least about 85 C., and centrifuging the dispersion to separate the wool wax therefrom.

2.. Process for the recovery of wool wax from froths produced from wool scour liquor as in claim 1; wherein said froth is produced from scour liquors resulting from the use of non-ionic detergent of the condensed ethylene oxide type.

3. Process for the recovery of wool waxrfrom froths.

produced from wool scour liquor as in claim 1; wherein said froth is produced from wool. scour. liquors resulting from the use of sulphated long chain alcohols as detergent.

4. Process for the recovery of wool wax' from froths produced from wool scour liquor as in claim 1; wherein said centrifuging to separate the wool wax from the dis.- persion is repeated.

5. Process for the recovery of wool wax from. froths produced from wool scour liquor as in claim 1; further comprising cooling the separated wool wax, reheating the separated wool wax, and again centrifuging the. reheated wool wax to reduce the moisture content of the latter.

6. Process for the recovery of wool, wax having an acid, number less than 1 from froths produced fromwool scour liquor resulting from the use of soap as the detergent, which comprises treating the froth with a dispersing agent selected from the group consisting of sodiumphosphates and potassium phosphates, addingmaterial to ad-,

the pH to a value ofat least approximately 9.8 is-sodium carbonate.

8. Process for the recovery of wool wax havingv an acid number between 1, and 2 from froths produced from wool scour liquor resulting from the use ofsoap: as the detergent, which comprises, treating the froth witha dispersing agent selected from the group consisting of sodium phosphates and potassium: phosphates, adding material to adjust the pH to a value of between approximately 9.8 and 9.3, heating the dispersion to a temperature ofv at leeast' about C., and centrifuging the dispersion to separate thewool wax. therefrom- 9. Processfor the recovery of wool'wax having an'acid number betweenl and 2 from'frothsproduced from woolv um phosphates and potassium phosphates, adding ma- 1 terial to; adjust the pH'to a value of between approximately 9.3 and 8.4, heating the dispersion to a temperature. of. at least about 85 C., and centrifuging the. dispersionto separate the wool wax therefrom.

11. Process for the recovery of wool wax having an acid number greater than 5 from froths produced from wool scour: liquor resulting from the use of soap as the detergent, which comprises treating the froth with a dis-- persing agent selected fromthe group consisting of. sodium phosphates and potassium phosphates,; adding material to adjust the pH to a value of less than approximately 8.4, heating the dispersiontoa temperature-of at least about 85. C., and centrifuging the'dispersion to; sep- I arate the woolwax therefrom.

References-Cited in the file of this patent UNITED STATES PATENTS 96,241. Koehler Oct. 26, 1869. 2,380,259 Pierce July 10, 1945 2,692,184 Cabot et a1. Oct. 19, 1954 FOREIGN PATENTS Great Britain, of 1855 

1. PROCESS FOR THE RECOVERY OF WOOL WAX FROM FROTHS PRODUCED FROM WOOL SCOUR LIQUOR, WHICH COMPRISES TREATING THE FROTH WITH A DISPERSING AGENT SELECTED FROM THE GROUP CONSISTING OF SODIUM PHOSPHATES AND POTASSIUM PHOSPHATES, HEATING THE DISPERSION TO A TEMPERATURE OF AT LEAST ABOUT 85*C., AND CENTRIFUGING THE DISPERSION TO SEP-ARATE THE WOOL WAX THEREFROM. 